In the production of cast iron bodies, i.e. castings from cast iron and especially relatively large castings, it is common practice to eliminate defects at the surface of such bodies by a finish welding or a repair welding. A finish welding is intended to fill recesses or eliminate inclusions or fill crevices or weak points, cracks or the like which can be considered incomplete portions of the casting or which are defects in regions which may affect the invention.
Repair welding is used to cure breaks or the like which may occur in handling or may result during the casting process, or to restore structural integrity of a casting otherwise.
The castings with which the invention is primarily concerned are castings of graphitic cast iron and especially spherolitic cast iron.
The castings are generally heavy machined parts, such as machine frames, chassis, bases, columns and posts, motor housings and the like, but also radiation shielding transport storage containers which are used to receive irradiated fuel elements and other radioactive substances and the requirements for such articles are quite severe and thus casting defects which may affect integrity must be scrupulously avoided or cured.
As has been suggested it is known to attempt to eliminate casting defects on the surface of a cast article by electric arc welding utilizing welding electrodes which are denominated cast iron electrodes, by suitable adjustment of the welding parameters. The welding is in effect a deposition welding with hand control of the welding rod. The repairs thus made are seldom completely reliable and do not satisfy all of the requirements for structural integrity.
Electric welding systems are available which have been used for cutting, i.e. so-called electric arc cutting "torches" for automatic electrode feed and automatic control of the energy supply (see the paper entitled Arc Air of the Arc Air Company of Lancaster, Ohio, 11-85. The electrode is surrounded by a blast air which blows the melt as it is formed away from the crevice or slot which is cut in the workpiece. These automatic cutting units are not, however, suitable for eliminating the casting defects on the surface of cast iron objects and in fact can destroy such objects.